A&P Chapter 6 Flashcards
What does the human skeleton initially consist of?
Cartilage, which later is replaced by bone
What is skeletal cartilage made of?
Highly resilient, molded cartilage tissue that consists primarily of water. Contains no blood vessels or nerves
What is the perichondrium?
Layer of dense connective tissue surrounding cartilage
What does the perichondrum do?
Helps cartilage resist outward expansion, contains blood vessels for nutrient delivery to cartilage
What is cartilage made of?
Chondrocytes, cells encased in small cavities (lacunae) within jelly-like extracellular matrix
What are the three types of cartilage?
Hyaline, elastic, and fibrocartilage
What does hyaline cartilage provide?
Support, flexibility and resilience
Where is hyaline cartilage located?
Joints, ribs, respiratory, and nasal cartilage
What is elastic cartilage?
Similar to hyaline cartilage, but contains elastic fibers
Where is elastic cartilage located?
External ear and epiglottis
What is fibrocartilage made of?
Thick collagen fibers that has great tensile strength
Where is fibrocartilage located?
Menisci of knee, vertebral discs
What two ways does cartilage grow?
Appositional growth, and interstitial growth
What is appositional growth?
Thickness, cartilage-forming cells in perichondrium secrete matrix against external face of existing cartilage. A new matrix is laid down on surface on cartilage
What is interstitial growth?
Length, chondrocytes within lacunae divide and secrete a new matrix, expanding cartilage from within. A new matrix is made within cartilage.
What are the functions of bones?
- Support = For body and soft organs
- Protection = Protects brain, spinal cord, and vital organs
- Movement =Levers for muscle actions
- Mineral and growth factor storage = Calcium, phosphorous, and growth factors reservoir
- Blood cell formation = Hematopoiesis occurs in red marrow cavities of certain bones
- Triglyceride storage = Fat, used for an energy source, is stored in bone cavities
- Hormone production = Osteocalcin, which is secreted by bones helps to regulate insulin secretion, glucose levels, and metabolism
How many bones are in the human skeleton?
206
What are the two groups of bones that are based on location?
Axial skeleton, and appendicular skeleton
What is the axial skeleton?
Long axis of the body, contains the skull, vertebral column, and rib cage
What is the appendicular skeleton?
Limbs, shoulder, and hip
What are the classifications of bones by shape, and what is an example of each?
- Long bone (humerus)
- Flat bone (sternum)
- Irregular bone (vertebrae)
- Short bone (talus)
Is a bone an organ? Why or why not?
Yes, because they contain different types of tissues
What tissues do bones have?
Bone (osseous) tissue predominates, but a bone also has nervous tissue, cartilage, fibrous, connective tissue, muscle cells, and epithelial cells in its blood vessels
What are the three levels of bone structure?
Gross, microscopic, and chemical
What is compact bone?
Dense outer layer on every bone that appears smooth and solid
What is spongy bone made of?
Made up of a honeycomb of small, needle-like or flat pieces of bone called trabeculae. Open spaces are filled with red or yellow bone marrow
What does short, irregular, and flat bones consit of?
Thin plates of spongy bone (diploe) covered by compact bone
Where is compact bone in short, irregular, and flat bones?
Sandwiched between connective tissue and membranes
What is the periosteum and endosteum?
The periosteum covers the outside of compact bone and the endosteum covers the inside portion of compact bone
Where is bone marrow in short, irregular, and flat bones?
Scattered throughout spongy bone, no defined marrow cavity
What does hyaline cartilage cover in short, irregular, and flat bones?
The area of bone that is part of a movable joint
What is the diaphysis of long bones?
Elongated, usually cylindrical shaft, provides leverage and weight support, compact bone with spongy bone extending inward
What is the medullary cavity in a long bone?
Hollow, cylindrical space within the diaphysis, contains red bone marrow in children, and contains yellow bone marrow in adults
What is the epiphysis in long bones?
Knobby region at the end of each bone, composed of outer thin layer of compact bone, and the inner region of spongy bone
What is the proximal epiphysis?
End of the bone closest to body trunk
What is the distal epiphysis?
End furthest from trunk
What is the articular cartilage?
Covers the joint surface, thin layer of hyaline cartilage, reduces friction, absorbs shock in moveable joints
What is the epiphyseal plate?
In metaphysis, also known as growth plate, has a thin layer of hyaline cartilage, provides for lengthwise bone growth
What is the epiphyseal line in adults?
The remnant of the epiphyseal plate
What is the periosteum?
White, double layered membrane that covers external surfaces except joints. It’s the anchoring points for tendons and ligaments
What does the periosteum contain?
Many nerve fibers and blood vessels that continue into the shaft through nutrient foramen openings
What is the endosteum?
Delicate connective tissue membrane covering the internal bone surface. Covers trabeculae of spongy bone. Lines canals that pass through compact bone
Where is red marrow found?
Within trabecular cavities of spongy bone and diploe of flat bones, such as the sternum
What is the difference of medullary cavities in newborns and adults?
In newborns, medullary cavities and all spongy bones contain red marrow, but in adults, the medullary cavities contain yellow marrow
Where is red marrow located in adults?
Head of the femur and humerus
Where is the most active areas of hematopoiesis in adults?
Flat bone diploe and some irregular bones (like the hip bone)
Can yellow marrow convert to red marrow? Why or why not?
Yes, if the person becomes anemic
What is a tuberosity?
Large, rounded projection, may be roughened
What is a crest?
Narrow ridge of bone, usually prominent
What is a trochanter?
Very large, blunt, irregularly shaped process
Where is the only location of the trochanter?
The femur
What is a line?
Narrow ridge of a bone, less prominent than a crest
What is a tubercle?
Small rounded projection or process
What is a epicondyle?
Raised area on or above a condyle
What is a spine?
Sharp, slender, often pointed projection
What is a process?
Any bony prominence
What is a head?
Bony expansions carried on a narrow neck
What is a facet?
Smooth, nearly flat joint suface
What is a condyle?
Rounded articular projection, often articulates with a corresponding fossa
What is a groove?
Furrow
What is a fissure?
Narrow, slitlike opening
What is a foramen?
Round or oval opening through a bone
What is a notch?
Indentation at the edge of a structure
What is a meatus?
Canal-like passageway
What is a sinus?
Cavity within a bone, filled with air and lined with a mucous membrane
What is a fossa?
Shallow, basin-like depression in a bone, often serving as an articular surface
What are osteogenic cells?
Also called osteoprogenitor, mitotically active stem cells in periosteum and endosteum
What happens when osteogenic cells are stimulated?
They differentiate into osteoblasts or bone-lining cells, some remain as osteogenic stem cells
What are osteoblasts?
Bone-forming cells that secrete unmineralized bone matric called osteoid
What are osteoids made up of?
Collagen and calcium-binding proteins. Collage makes up 90% of bone protein
Osteoblasts are ______ mitotic
Actively
What are osteocytes?
Mature bone cells in lacunae that no longer divide. They maintain the bone matrix and acts as stress or strain sensors
What do osteocytes respond to?
Mechanical stimuli such as increased force on bone or weightlessness
What do osteocytes communicate information to?
Osteoblast and osteoclasts so bone remodeling can occur
What is an osteoclast cell?
Cells that destroy bone
What are bone-lining cells?
Flat cells on bone surfaces believed to also help maintain the matrix, along with osteocytes
On the external bone surface, lining cells are called _________
Periosteal cells
On the internal surface, lining cells are called _________
Endosteal cells
What are osteoclats?
Derived from the same hematopoietic stem cells that become macrophages. They are giant, multinucleate cells that function in bone resorption
What characteristic do osteoclast cells have?
The cell has ruffled borders that serve to increase surface area for enzyme degradation of bone. It also helps seal off the area from the surrounding matrix
What does compact bone consist of?
Osteon, canals, canaliculi, interstitial lamellae, and circumferential lamellae
What is an osteon?
The structural unit of compact bone that consists of an elongated cylinder that runs parallel to the long axis of bone. They act as tiny weight-bearing pillars
What does an osteon cylinder consist of?
Several rings of bone matric called lamellae
What does lamellae contain and what does it withstand?
Lamellae contain collagen fibers that rub in different directions in adjacent rings. Bone salts are found between collagen fibers
Where does the central canal run through?
The core of the osteon
What does the central canal contain?
Blood vessels and nerve fibers
What are perforating canals?
Canals lined with endosteum that occur at right angles to the central canal
What do perforating canals connect?
Blood vessels and nerves of the periosteum, medullary cavity, and the central canal
What are lacunae?
Small cavities that contain osteocytes
What is canaliculi?
Hairlike canals that connect lacunae to each other and to the central canal
What do osteoblast that secrete bone matrix maintain contact with?
Each other and osteocytes via cell projections with gap junctions
What happens when the matrix hardens and cells are trapped in the canaliculi form?
Allows communication between all osteocytes of the osteon and permits nutrients and wastes to be relayed from one cell to another
What is interstitial lamellae?
Lamellae that are not part of the osteon. Some fill gaps between the forming osteons, and others are remnants of osteons cut by bone remodeling
What is circumferential lamellae?
Just deep to the periosteum, but superficial to the endosteum. These layers of lamellae extend around the entire surface of diaphysis. They help the long bone to resist twisting
How does spongy bone appear?
Appears poorly organized but is actually organized along lines of stress to help bone resist any stress
What do trabeculae do?
Confer strength to bone, like cables on a suspension bridge
Are osteons present in trabeculae?
No osteons are present, but trabeculae do contain irregularly arranged lamellae and osteocytes interconnected by canaliculi
How is the trabeculae nourished?
Capillaries in endosteum supply nutrients
Bone is made up of ________ and ______ components
Organic and Inorganic
What are the organic components of bone?
Includes osteogenic cells, osteoblasts, osteocytes, bone-lining cells, osteoclasts, and osteoid
What are osteoid secreted by?
Osteoblasts
How much of the organic bone matrix is made up of osteoids?
One-third
What do osteoids consist of?
Ground substance and collagen fibers, which contribute to high tensile strength and flexibility of bone
What are the inorganic components of bone?
Hydroxyapatites (mineral salts)
What percentage does hydroxyapatites make up bone by mass?
65%
What does hydroxyapatites consist of?
Tiny calcium phosphate crystals in and around collagen fibers
What are hydroxyapatites responsible for?
Hardness and resistance to compression
What is osteogenesis (ossification)?
The process of bone tissue formation
What are the different ossifications in development?
Formation of the bony skeleton begins in month 2 of development, postnatal bone growth occurs until early adulthood, and bone remodeling repair are lifelong
What is the formation of the bony skeleton?
Up to about week 8, fibrous membranes and hyaline cartilage of the fetal skeleton are replaced with bone tissue
What is endochondral ossification?
Bone forms by replacing hyaline cartilage. Bones are called cartilage (endochondral bones), they form most of the skeleton (long bones). Mesenchymal cells specialize into osteoblasts. Begins at the primary ossification center
What is intramembranous ossification?
Bone develops from fibrous membrane. Bones are called membrane bones. Flat bones of skill, some facial bones, and part of the clavicle
Long bones grow lengthwise by __________ growth of the ________ plate
Interstitial (longitudinal) of the epiphyseal plate
Bones increase thickness through ________ growth
Appositional
Bones stop growing during _______ but some ________ continue to grow slowly through life
Adolescence, facial bones
Near the end of adolescence _______ divide less often
Chondroblasts
What occurs at the end of adolescence?
Epiphyseal plate thins, then is replaced by bone. The epiphyseal plate closure occurs when the epiphysis and diaphysis fuse
When does bone lengthening stop?
Females = around 18 years of age
Males = occurs around 21 years of age
Growing bones widen as they lengthen through __________
Appositional growth
Bones _______ in response to increased ______ from muscle activity or added weight
Thicken, stress
Osteoblasts beneath the periosteum secrete bone matrix on _______
External bone
Osteoclasts ________ bone on _______ surface
Remove, endosteal
Usually, there is more _______ than _______ which leads to _________
Building up, building down, stronger bones that are not too heavy
What is growth hormone’s role in bone growth?
Most important hormone in stimulating epiphyseal plate activity in infancy and childhood
What is thyroid hormone’s role in bone growth?
Modulates activity of growth hormone, ensuring proper proportions
What does testosterone and estrogens at puberty do for bone growth?
Promote adolescent growth spurts and ends growth by inducing epiphyseal plate closure
What does calcitonin and parathyroid hormone do for bone growth?
Control blood calcium levels by inhibiting (calcitionin) or promoting (PTH) osteoclast activity
What percentage of bone mass is recycled each week?
5-7%
How long does it take for spongy bone to be replaced?
3-4 years
How long does it take for compact bone to be replaced?
Every 10 years
What does bone remodeling consist of?
Both bone deposit and bone resorption
New bone matrix is deposited by ___________
Osteoblasts
Resorption is the function of _________
Osteoclasts
Bone remodeling occurs at _______
Surfaces of both periosteum and endosteum
What is the PTH control of blood calcium levels?
Calcium homeostasis of blood: 9-11mg/100 mL is the balance —> then the stimulus is falling blood Ca^2 levels –> then the parathyroid glands release parathyroid hormone –> parathyroid hormone goes up –> osteoclasts degrade the bone matrix and releases Ca^2 into blood
What is hypocalcemia and what does it cause?
Low levels of calcium cause hyperexcitability
What is hypercalcemia and what does it cause?
High levels of calcium cause nonresponsiveness
What can sustained high blood calcium levels lead to?
Deposits of calcium salts in blood vessels or kidneys and the formation of kidney stones
Most fractures result from trauma in what age group?
Youth
Most fracturs result from weakness of bone due to bone thinning in what age group?
Old age
What are the three either/or fracture classifications?
Position of bone ends
Completeness of break
Whether skin is penetrated
What is the position of bone ends after fracture classification?
Nondisplaced = ends retain normal position and displaced = ends are out of normal alignment
What is the completeness of break classification?
Complete = broken all the way through and incomplete = not broken all the way through
What is the whether skin is penetrated classfiication?
Open (compound) = skin is penetrated and closed (simple) = skin is not penetrated
What is comminuted fracures?
Bone fragments into three or more pieces, it’s particularly common in the aged, whose bones are more brittle
What is a compression fracture?
Bone is crushed, it’s common in porous bones (osteoporotic bones) subjected to extreme trauma, like in a fall
What is a spiral fracture?
A ragged break occurs when excessive twisting forces are applied to a bone, it’s a common sports fracture
What is a epiphyseal fracture?
The epiphysis separates from the diaphysis along the epiphyseal plate. It tends to occur where cartilage cells are dying and calcification of the matrix is occuring
What is a depressed fracture?
A sad fracture :(
Actually a broken bone portion that is pressed inward, it’s typical of a skull fracture
What is a greenstick fracture?
The bone breaks incompletely, much in the way a green twig breaks. Only one side of the shaft brakes, the other side bends. It’s common in children, whose bones have relatively more organic matrix and are more flexible than those of adults
What is the fracture repair sequence?
- A hematoma forms
- Fibrocartilaginous callus forms
- Bony callus forms
- Bone remodeling occurs
Imbalances between bone deposit and bone resorption underlie __________
Nearly every disease that affects the human skeleton
What are the three major bone diseases?
Osteomalacia/rickets, osteoporosis, and Paget’s disease
What is osteomalacia?
Bones are poorly mineralized, osteoid is produced, but calcium salts are not adequately deposited. It results in soft weak bones and causes pain upon bearing weight
What is rickets?
Osteomalacia of children. It results in bowed legs and other bone deformities because bone ends are enlarged and abnormally long. It’s caused by vitamin D deficiency or insufficent dietary calcium
What is osteoporosis?
A group of diseases in which bone resorption exceeds deposit. The matrix remains normal, but bone mass declines. The spongy bone of the spin and neck of the femur are most susceptible. Vertebral and hip fractures are common
What are the risk factors for osteoporosis?
Most often aged, postmenopausal women. Affects 30% of women aged 60-70 years and 70% by age 80. Estrogen plays a role in bone density, so when levels drop at menopause, women run higher risk. Men are less prone due to protection by the effects of testosterone
What are additional risk factors for osteoporosis?
Insufficient exercise to stress bones, diet poor in calcium and protein, smoking, genetics, hormone-related conditions like hyperthyroidism and diabetes mellitus, and consumption of alcohol or certain medications
What is the treatment for osteoporosis?
Calcium, vitamin D supplements, weight bearing exercises, HRT (slows bone loss but does not reverse it, and is controversial because of increased risk of heart attack, stroke, and breast cancer_
What is Paget’s Disease?
Excessive and haphazard bone deposit and resorption cause bone to grow fast and develop poorly. The bone is called Pagetic bone. There is a very high ratio of spongy to compact bone and reduced mineralization. It usually occurs in the spine, pelvis, femur, and skull. It rarely occurs before age 40. The cause is unknown, possibly viral.
What is the treatment for Paget’s Disease?
Calcitonin and bisphosphonates
Most long bones begin by _______, with primary ossification centers developed by ________
8 weeks, week 12
At birth, most long bones are _______
Ossified, except at epiphyses
Epiphyseal plates persist through _______
Childhood and adolescense
When are all bones completely ossified, and when skeletal growth ceases?
~25 years of age
What is Osgood-Shlatter’s disease?
Common cause of knee pain in growing adolescents. It’s inflammation of the area where the patellar tendon attaches to the tibia (tibial tuberosity). It usually resolves on it’s own
What is achondroplasia?
Congenital condition involving defective cartilage and endochondral bone growth. The limbs are too short, but the membrane bone are normal size. It’s a form of dwarfism
What is acromegaly?
When your pituitary gland produces too much hormone during adulthood. It’s usually caused by a noncancerous tumor. it causes enlargement of the bones in the face, hands, and feet
